Thinkom products achieve dual circular polarization at Ka-band using PCB-based approaches, generally using a Variable Inclined Transverse Stub, or “VICTS” approach with two types of mechanical rotation. The first type rotates one array relative to another, and the second type rotates both in azimuth. The primary limitations are scan range (Elevation between 20 and 70 degrees, no broadside possible) and beam performance (sometimes limiting to Rx only).
Ando et al., “Radial line slot antenna for 12 GHz DBS satellite reception”, and Yuan et al., “Design and Experiments of a Novel Radial Line Slot Antenna for High-Power Microwave Applications”, discuss various antennas. The limitation of the antennas described in both these papers is that the beam is formed only at one static angle. The feed structures described in the papers are folded, dual layer, where the first layer accepts the pin feed and radiates the signal outward to the edges, bends the signal up to the top layer and the top layer then transmits from the periphery to the center exciting fixed slots along the way. The slots are typically oriented in orthogonal pairs, giving a fixed circular polarization on transmit and the opposite in receive mode. Finally, an absorber terminates whatever energy remains.
“Scalar and Tensor Holographic Artificial Impedance Surfaces”, Authors Fong, Colburn, Ottusch, Visher, Sievenpiper. While Sievenpiper has shown how a dynamic scanning antenna would be achieved, the polarization fidelity maintained during scanning is questionable. This is because the required polarization control is dependent on the tensorial impedance required at each radiating element. This is most easily achieved by element-wise rotation. But as the antenna scans, the polarization at each element changes, and thus the rotation required also changes. Since these elements are fixed and cannot be rotated dynamically, there is no way to scan and maintain polarization control.
Industry-standard approaches to achieving beam scanning antennas having polarization control usually use either mechanically-rotated dishes or some type of mechanical movement in combination with electronic beam steering. The most expensive class of options is a full phased-array antenna. Dishes can receive multiple polarizations simultaneously, but require a gimbal to scan. More recently, combining of mechanical movement in one axis with electronic scanning in an orthogonal axis has resulted in structures with a high aspect ratio that require less volume, but sacrifice beam performance or dynamic polarization control, such as Thinkom's system.
Prior approaches use a waveguide and splitter feed structure to feed antennas. However, the waveguide designs have impedance swing near broadside (a band gap created by 1-wavelength periodic structures); require bonding with unlike CTEs; have an associated ohmic loss of the feed structure; and/or have thousands of vias to extend to the ground-plane.